Grinding wheel and wheel diameter measuring apparatus



L.- cogs, JR

Aug. 2, 196Q Filed March 25, 1959 RESISTANCE B W 2 mm J m w am m 0 m5 n my m W F Im A... MC M 7 m m W... L a MM II n:

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'RHEOSTAT United States Patent GRINDING WHEEL AND DIAMETER MEASURING APPARATUS Loring 'Coes, Jr., Brooldfield, Mass., assignor to Norton Clpmpany, Worcester, Mass a corporation of Massac usetts Filed Mar. 25, 1959, Ser. No. 801,930 22 Claims. (Cl. 51-1345) The invention relates to grinding wheels and wheel diameter measuring apparatus.

One object of the invention is to control snagging grinders for more efficient grinding. Another object is to achieve the foregoing by periodically increasing the speed of the grinding wheel but without risking over-speeding it. Another object of the invention is to inform theoperator when the surface speed of the grinding wheel has dropped by a certain increment. Another object is to enable the operator then to speed the grinding wheel and.

to be told when he has speeded it up enough and should speed it no more because of danger of breakage.

Another object is to measure the diameter of a grinding'wheel without stopping its rotation. Another object is to achieve the foregoing object accurately in a practical manner. Another object is to achieve the foregoing with inexpensive apparatus.

Another object of the invention is to provide signal devices showing when the grinding wheel is going too slowly and when it is. going too fast so that the operator can adjust the wheel speed within these limits or stop adjusting it when the too fast signal lights because that will be set only at the threshold of too fast and will soon go out. This is the simpler embodiment of the invention but another object is to maintain the grinding wheel operating at a constant peripheral speed or nearly so. With the grinding wheel operating at a constant peripheral speed, its factor of safety against wheel breakage doesnt vary much and due to the presence of the central hole, it rises slightly. Another object of the invention is to provide an adjustment so that the operator can adjust the controls to increase the peripheral speed as the wheel gets smaller in order to grind more efliciently without danger as the factor of safety would otherwise increase.

Other objects will be in part obvious or in part pointed out hereinafter. V

In the accompanying drawings illustrating four of many possible embodiments.

Figure 1 is a diagrammatic view showing automatic controlling apparatus for increasing the speed of a grinding wheel responsive to reduction of its diameter due to grinding, showing the grinding wheel in section,

Figure 2 is a circuit diagram showing a modification of a part of the circuit of Figure 1 whereby one indicator operates when the wheel is running too fast and another one when the wheel is running too slowly, Figure 3 is an elevation of the grinding wheel, Figure 4 is an axial sectional-view of a modification of the grinding wheel of the invention for use with the same controls.

Figure 5 is a cross sectional view taken on the line 5-5- of Figure 4.

Figure 6 is a radial sectional view of another embodiment of the grinding wheel of the invention for use with the same controls, part of the wheel being shown 1n elevation and-parrot the wheel being'cut off to save space. i Y

' ging machines.

7 "2,947,121 l atented 2, 1960 ment of the grinding wheel of the invention for use with the same controls, part of the wheel being shown in elevation and part of the wheel being cut oil to save space.

In modern steel mill practice, stainless steel slabs and billets are conditioned for rolling on remote control snagperipheral speed of the grinding wheel must be maintained at as high a value as safety permit. To do this without stopping the machine is an object of the invention. The way it is done is by keeping constant track of the diameter of the wheel.

Various electrical, optical, and mechanical means for doing this have proved impractical, because of the large amount of dust and grinding swarf surrounding the wheel and because of vibration of the wheel or for other reasons. I have invented a way to keep constant track of the diameter of the wheel by incorporating in the wheel a resistance device the electrical geometry of which changes as the wheel diameter changes.

Referring to Figure l, a grinding wheel 11, for example made out of abrasive bonded with phenolic resin,

. which is connected to an aluminum ring 18. All these aFi'gureJ is: a radial sectional-viewofanother embodi parts are molded into the wheel.

The wheel is mounted on a spindle 2 1 and secured thereon by a nut 22. A shoulder 23 of the spindle 21 is in contact with the ring 16. The spindle 21 is journalled in a bearing 25 supported by the snagging machine or other grinder. Keyed to thespindle 21 as by means of a key 26 is a pulley 27 driven by belts 28 from a pulley 29. on a motor shaft 30 of a'wheel driving motor 3 1. This motor 31 is driven by positive line 32. to a brush 33 through a commutator 34 to a brush 35 to the negative line 36. V

A tachometer generator 41 has a drive shaft 42 with a tachometer connection 43 driven by the wheel spindle 21. The positive side of the generator 41 goes to a line 44 to a relay coil 45 to a line 46 to a relay coil 47 through line 48 to a relay coil 49 to a line 50 to a brush 51 contacting the ring 18. The current then goes to the bar 14 through the resistance I12 to the bar 13 to the copper ribbon 15 to the ring 16 to the spindle 21 to the cone 43 to a brush 52 to a of the generator 41. i

The relay 45 controls a normally closed switch. 55 which connects a line 56 from line 32 to a line 57 which line 53 to the negative side goes to line 36. When the generator 41 fails to deliver.

close. The solenoids of the relays 47 and 49 are as in the usual case balanced ,by springs which can be adjusted Such relays are available-on the market.

Positive line 71 is' connected to line 72 leadingto one terminal of the switch 62. They other terminal of the switch 62, is connected by a line 73 to a field coil 74 of a moto r ,75. I-Ieg ative' line 76 is connected to a hand switch 77 to line 78 which leads to the other end; of the field coil '74 shown at the bottomdiagrammatically and For maximum grinding economy, the

This allows the switch'61, to close. Should this action increase the speed of the grinding wheel too much, the relay switch 62 would.

3 also to a line which goes to one end, shown diagrammatically as the upper end of a field coil 81 the other end of which is connected by a line 82 to one terminal of the switch 61. the other terminal of which is connected to positive line 71. Obviously the lines 32 and 71 could be. connected to the same positive pole of a D.C.'battery or D.C.- generator and the lines 36 and 76 could be connected to the same pole of a DC. battery or generator.

.Positive line 71 is connected by a line 85 through a switch 86 :to a line 87 .to abrush 88 to a commutator 90 on the armature shadit 91 of the motor 75. The commutator 90 is, also contacted by a brush 93 which is connected to a line 94 leading to the negative line 76.

. The commutator shaft 91 of the motor 75 is connected to. a speed reducing gear the output end of which is connected by ashaft 101 to the rotatable element 102 of a .rheostat 103. The rheostat 103 is connected on the input end by lines 104 and 105 to the lines 32 and 36 respectively. The .oiutputend of the rheostat 103 is connected by lines 106.. and 107 to the field coil of the motor 31 which is a DC. motor.

The motor 75 is a reversing motor and when the grinding wheel. has worn. away some to close the switch 61, it moves in such. a directionas to cause the rheostat 103 to decrease the voltage to the wheel motor 31 thus speeding it up. If it speeds up too much, the switch 62 closes and the motor 75 through the reducing gear 100 turns the rheostat 103 in the other'direction to slow down the motor 31. The point of balance is reached when both switches 61 and 62 are open until the wheel 11 is worn away some more. For hand operation of the rheostat 103 I show theshaft 101 broken into two parts which can be coupled by a coupling 110. When uncoupled the element 102 can be operated by a shaft 111 and a knob 112.

For manually controlling the apparatus in response to signals and by means of the knob 112, I show the simple circuit of Figure 2. The relays 47 and 49 are indicated and the connections above them are the same. The apparatus of Figure 2 is also the same above this level on. the drawing. The relay switches 61 and 62 are shown. Line 71 is connected to one terminal of the switch 61 as in the first case and line 76 is connected by lines 115 and 116m lights 117 and 118 respectively. The other terminal of light 117 is connected by a line 120 to the other terminal of switch 62 and the other terminalof light 118 is. connected by a line 121 to the other terminal of switch 61. .It will now be seen that if the wheel motor 31 runs too fast, the light 117 will light and if it runs too slowly the light 118 will light. A variable 'resistor125. is provided in the line 44 for adjustment.

The grinding wheel of the invention can be made out of any abrasive but aluminum oxide abrasive, regular grade,.is preferred. While the grit sizes may be various, for most snagging operations 14 grit size is preferred. While many bonds might be used, the organic bonds will withstand higher speeds and of these, phenolic resin is preferred. A satisfactory combination is BR9332 liquid resin to wet the abrasive grains and to pick up the powdered uncured .resin BR2417. A, good proportion of these is 25% of the liquid resin. and 75% of the powdered resin by weight; A good wheel structure is 60% abrasive and 40 volume percent bond; Wheel molding and curingis now so well knownand has been written into so. many patents that I need not describe it.

There is no problem involved. in molding the resistance 12, the bars.13 and 14, the ribbons '15 and 17 and the rings 16 and 18 into the wheel. This simply requires care .and careful levelling of themix from time to timeby the. wheel molder.

. It is true thatasingleresistance with connecting parts inone radius of the wheel. will slightly unbalance it. Remedyis taprovidetwoof:them which can easily be done. However, this is unnecessary since the unbalance is very slight and grinding wheels doing snagging operations vibrate anyway.

Referring now to Figures 4 and 5, in this modification or embodiment of the invention, in the grinding wheel 11a the aluminum bars 13 and 14 are provided connected by the copper ribbons 15' and 17 to the aluminum rings 16 and 18. However, instead of the thin strip of carbon for a resistance element, 1 provide wire coil resistors 12a. extending between the bars 13 and 14. Thus as each resistance coil 12a is cut, the resistance between the bars 13 and 14 is increased. Thus in the embodiment of Figure 4, the resistance goes up by increments rather than continuously, but this is no detriment. 'Ihe coils 12a of Figure 4 can be made out of many different metals and alloys but a satisfactory one and the one now preferred by me is Nichrome. The best one for the resistance wire 12a I believe to be 75 Ni, 12 Fe, 11 Cr and 2 Mn.

Referring now to Figure 6, the grinding wheel 11b has the same aluminum rings 16 and 18 embedded therein as in the other cases.- Embedded in the wheel 11b is a resistance wire 12b, preferably made out of the same Nichrome and'preferably of zigzag shape as shown to increase its electrical length and extending as far around the grinding wheel as desired for it could even extend beyond 360 degrees by being slightly out of a plane perpendicular to the axis of the grinding wheel. One end of the resistance wire 12b is connected by a copper ribbon 15b to the ring 18 and the other end of the resistance wire 12b is connected by a copper ribbon 17b to the ring 16. Snunt loops of low resistance material such as copper of any desired cross section (and the conductors 15b and 17b canbe of any desired cross section too) are connected to shunt out portions of the resistance wire 12b as shown. As also shown they extend to varying distances from the original periphery of the wheel. As each one is broken, the total electrical resistance in the wheel is increased, step by step. Although these shunts are shown as arranged-in order ofvdiminishing. radius, they can be in any order of radius whatsoever. ures 4 and 5 on the one hand and Figure 6 on the other hand operates the controlling apparatus of Figuresl and 2m the same way, no change being needed, for either embodiment, in the controlling apparatus.

Referring now toFigure 7, the grinding wheel 11c has the same commutators 16 and 18 embedded therein and connecting conductors 15c and as shown, each one connected to one end of a flat, partly circular resistance 120, which may be made-of the same Nichrome and is preferably quite thin to give a large resistance in view of the fact that it is so wide. However, the variable resistor 125v can have such resistance values that the resistance 120 can have fairly low resistance at the start. Just. as an example, thisthin sheet of metal which makes the partly circular resistor 120 can be .010 inch thick, but it can vary Widely from that in either direction. In order that it shall not. produce a weakness in the wheel 11c holes 131 are. punched through it throughout its area. This. resistor 12c could extend more than 360 degrees around the wheel by molding it in the wheel out of the plane perpendicular to the axis thereof, and it could be much shorter circumferentially' than shown.

. It will now be seen that as the wheel 1 1a wears away, the electrical resistance through the wheel increases rather than diminishes. Nevertheless this wheel 11c can bev used with the controlling apparatus of Figures 1 and 2 only the rheostat 103 will be set in the reverse manner to decrease the currentrunning through the lines 106 and 107 tothe field coils of the motor 31 when the resistance through the wheel 11c increases.

The rings 16 and' 18 are' commutators and need not even be continuous if extra connections 15 and 17 areprovided. to them fromztheelectricalends of the various Each of the embodiments of Fig 11b a 1 c.

Insteadofmsing electrical. connectionsi and 17 etc., the endsof-thei resistances can inmanycases be directly.

connected to. the commutators;- For instance, this woul be easy in the wheel of Figure 6; .1

,Besides phenolic --resin .for the bond, other organic bonds ,canbeused. For some purposes analine for-male dehyde :.,P0lymer might be .evenbetter than phenolic resin. Rubber, either natural or synthetic, could be used for many grinding operations.

,In Figure .4. the resistance coils 12a. could'be more or less str'aightwires. or couldbelrods. These are other embodiments of theinvention so in claiming the structure of Figure '14. I. will refer toaiseries of resistors extending in parallelbetween conductor bars.. In paralleli-means electricallyrin parallel as thecoils 12a are electrically in parallel. In :Figure 6 the resistance deviceincludes the Shl1l1t-llO0PS.. v130 because they'constitute operative parts:

ofthe device. 3 In Figures. 1 and4 the conductor bars :13 and 14 -are parts of the-electrical resistance device.

-.It willxbe' remembered that in the objectsit is stated that?the'zgriiidingwheelicanbe operated at an. increasing surface speed as iit 'iswo'rn away. This can readily be doneaby operating the variable resistance 125. Written instructions can.lie-provided tothe operator showing safe limits of operation: and for this purpose the size of the grinding' wheeh can be'accurately enough-measured by elapsed timeli adjustment can be made either when usingthe controls of Figurel or'the controls of Figure 2.

It is diflicult to make a choice of the best'inode of the:

various :features hf the invention; For the grinding wheel and resistance device thereis not much to choose between Figures 1, 4'and If for anyreason it is desired that the resistance should increase 1 during f grinding, the ern-' bodiment of Figure 7 will be chosen. For purposes of complying with the statute-, 'llchoose'the' embodiment of Fi f 'dgfu 1v f5 .gp v

Whetherto choose-the embodiment of the controls of Figure l or of Figure 2 is""a matter of-economics, convenience,'the siz e and-styleof the snagging grinder and so many other meters- 111s to make *it utterly impossible to choosebetween them. However,1insomuch as it is automatic, Ichoose the controls' of Figure 1- as the best mode tofcomply with' thdstatute. v

.It' willfre'adily-be seen that "the switches '61 and 62 areof opposite kindsg 61 being -'anormally closed switch and 62 being a 'normally' open switch. They are "both shown o'p'en' because 'that is the way they are during g'rinding-except'when adjustment is being made or a light is lit; "'Ihe switch62 is a' saftydevice and normally will not operate at all belcausje'a's' soon as the wheel motor 31 has been speeded by onlyjai'small amount the'switch 61 will open again befor'e theswitch 62 is closed. But in theembo'diment o'f Figure 2 -the"operator can use the switch 62 to s'et'a highe'r' limit if he desiresrather' than that set by the extinguishing of the light 118. In the claims I refer to the electrical geometry of the resistanceaadevicei 'fIt is :theKelectricalv geometry that counts. For exampletworesistorsmade of the same material can have the same resistance if the crosssectijoiial area one"is"twice that "of the {other andthefi other is helf'iis lo'ng the one? Alsoiii Figure 6 the physical geometry of the resistance wire 12b is never changed but the electrical geometry of the total resistance device is changed from time to time by the breaking of the shunt loops 130.

It will thus be seen that there has been provided by this invention a grinding wheel and a grinding machine which together measure continuously or from time to 6 time the diameter of the wheel in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved.

As many possible embodiments maybe made of the above invention and as many changes might be made in the embodiments above set forth, it is to be understood that; all matter hereinbefore set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

l claimz I I .l. A- grinding wheel consisting of abrasive grains bonded by organic bond and containing embedded thereinv an electrical resistance device, and containing at least partially embedded therein and each extending to a surface thereof a pair of commutators connected to the resistance device, the resistance device being so connectedto the commutators and so arranged in the wheel thatas the wheel is worn away during grinding the electrical geometry ofther'esistance device is changed and therefore the electrical resistance between the commutators is also changed. 2' A grinding wheel according to claim 1 in which the organic bond isphenolic resin.

3. A grinding wheel according to claim 1 in which the resistance device includes a strip resistance having sides and ends, the sides being connected to the commutators and one end of the resistance being farther from the center of the'wheel than the other end of the resistance.

4. A grinding wheel according to claim 3 in which the organic bond is phenolic resin.

l 5. A grinding wheel according to claim 1 in which the resistance device is a series of resistors extending in parallel between conductor bars which are at least partially embedded in the wheel, the bars being connected to the commutators, and the resistors being located progressively nearer to the center of the wheel. a

.6. A grinding wheel according to claims in which the organic bond is phenolic resin.

grinding iwheel according to claim 1 in which the resistance device is a resistance wire connected to the commutators and having shunt loops of low resistance materialfconnected to shunt out portions of the resistance wire said shunt loops extendingto varying distances from the-center; of the wheel.

8. A'grinding wheelfaccording to claim 7 in which the 1 resistance the ends of which are connected to the commutators and one side of which is fartherfrom the center of thewheel than the other side, whereby as the grinding wheel is worn the electrical resistance between the com mutatorsjs' gradually increased. g f

10. Agrinding wheel according to claim 9 in which the organic bond is phenolic resin.

:11. A grinding machine comprising a grinding wheel consisting of abrasive grains bonded by organic bond and containing embedded therein an electrical resistance device, andcontaining' at least partially embedded therein and each extending to a surface thereof a pair of commutators 'connectedto the resistance device, the resistance device'being so connected to the cornmutators and so arranged in the wheel that as the wheel is worn away during grinding the electrical geometry of the resistance device is changed an d therefore the electrical resistance between th commutators is also changed,'an electric motor. having at Ieastfone coil connected to rotate said grinding wheel, a generator connected to said motor to be driven by it, and electrical means connected to said generator and to said coil constructed to change the current through the coil responsive to changes in the value of the resistance of the resistance device.

12. A grinding machine according to claim 11 in which the resistance device is of such kind and so arranged in the wheel that as the wheel is worn away during grinding in which i the electrical resistance-between the commutators increases.

13. Agrindinginachine'comprisinga'grinding wheel consistingof abrasive grains bonded by organic bondand containingembedded therein an electrical resistance device, andcontaining at least partially embedded-therein and each extending toa surface thereof a pairof commutators connected to the resistance device, the resistance device being so connected to the commutatorsand so arranged in the wheel that as the wheel is worn away duringgrinding the electricah-geom'etry of the resistance device is changed and-therefore the' electrical resistance between the commutators is alsochanged, an electric motor having at least one coil connectedtorotatesaid grinding wheel, agenerator connected to said motor to be driven -by it, an electrical connectionbetween said generator and one ofjsaid commutators, a relay coil, a relay switch operated by said relay coil, an electrical connection between said generator and said relay coil, another electrical connection betweensaid relaycoil' and the other of said commutators, a second electric motor, at least one coil in said second electric motor, a rheostat connected to be operated by. said second motor, electrical connections betweensaid rheostat and the coil of the first mentioned electric motor, electrical power and connections connecting the coil of the second electric motor to the relay switch, and electric power connected to the rheostat.

14. A grinding machine according to.claim 13 in which there is a second relay coil between'said generator, the other of said comrnutators and a secondrelay' switch operated by said second relay coil and a second coil in the second electric motor, said second relay switch being connected to said second coil in the second electric'motor and said switches being of opposite kinds and one of said switches being a safety device.

15. A grinding machine comprising a grinding wheel, a first electric motor connected to said grindingwheel to rotate it said first electric motor having. at-least one coil, a generator connected to said motor'to be driven thereby, a rheostat connected to the coil of first electric motor said rheostat being also connected to electric power, a second electric motor connected tosaidrheostat, at least one coil in said second electric motor, a relay coil, a relay switch connected to be operated by'said relay coil, electrical connections from the relay switch to the coil in the second motor also connected to electrical power, an electrical resistance device embedded in the grindingwheel extending from place to place in thegrinding wheel one of which places is nearer to the center of the wheel than the other one is, and electrical connections from the resistance device to the generator and to the relay coil, whereby as the wheel is worn away during grinding the resistance value of the resistance device changes and the rotational speed of the wheel is changed.

-16. A- grinding machine according to claim 15 in which there is a second relay coil between said generator and said resistance device, a second relay switch operated by said second relay coil and a secondcoilin the second electric motor, said second relay switch being connected to said second coil in the second electric motor and said switches being of opposite kinds and one, of said switches being a safety device.

17. A grinding machine comprising agrinding wheel consisting of abrasive grains bondedrby-organic bond and containing embedded ther in n electrical resistance device, and containing at-least partially Y embedded therein andeach extending to a -surface thereof a pair of-commutators connected to the resistance device, the resistance device being so connected'to the commutators and soarranged inthe wheel that as the wheel-'is-worn away .during. grinding the electrical geometry of the resistance device is changed and therefore theelectrical resistance .between the commutatorsis also changed, and electrical:apparatus-outside of said wheel connected to said commutators and adapted tomeasure the electrical resistance between the commutators.

18. A grinding machine according to claim 17 in which the electrical apparatus gives. asignal every time the electrical resistance between the commlitatorshas changed by a certain increment,

19. A grinding machine comprising a-grinding wheel consisting of-abrasive g'rains: .honded by organic bond and. containing embedded therein an-electrical resistance device, and containing at leastrpartially. embedded therein and each extending to asurface thereof .a pair of commutators connected to. the resistance device, the resistance device. being. so. connected: to. the commutators' and so arranged in the Ivvheehthat'sas the wheel is worn away during grinding theelectrical geometryof the resistance device is changed and therefore the electrical. resistance between the; QOIDIIlUtfitOISxlSJ also, changed, an electric motor connected; to rotate-said grindingwheel, agenerator connected to, said-motor-to be; driven by it, an .electrical-connection betweensaida generator and, one of said commutators,.aurelayscoil, a relays'witch operated by saidrelay= coil, .an:.electrical=. connection between said generator andsaid, relay coil and the. other of 'said commutators, and a; signal device. connected'to power and to said relay; switch to. give .acsignal -when the electrical resistance between thencomrnutators has changed by a given amount.

20. A grinding machine according: to claim1.19- in which thereis asecond; relay coil; connected the same as the other relay coil and a secondg relay switch operated by said second relay'coilj' and Ma secondsignaldevice.connected to power and ;.t9.:said 5s.e.cond -;relay switch and the relay switches areofopposite kinds.

21. A grinding machine comprising a grinding wheel, an electric;m0t0r connected -to .isaid-, .grinding-wheel to rotate it, a generator connected to said motor to be driven thereby, an. electrical resistance deviceembedded in the grinding wheel extending from pl aee -.to, place in .the grinding wheel one of which places is nearer to the and the electrical resistance .device,;a second relay Switch operated by said second relay coil,.said second relay coil and said second relay switch. being, both connected to power, and a signal ,deviceconnected to-said second relay switch and topower, the two switches beingof opposite kinds.

References Cited :in the file of this patent UNITED STATES PATEN'IS 1,871,752 .Simonds Aug. 16, 1932' 1,880,492 Ruhlemann I., Oct. 4,- 1932 

